In general, a structure in which plural rotor blades are coupled by covers (snubber cover) integrally provided at blade top parts is used in a turbine rotor blade to suppress vibration generated during operation or to prevent steam from leaking out of the blade top part. This structure is known as a blade fastening structure enabling so-called a whole periphery integral blade.
A lot of arts studying about applicability of a shape of the cover, a degree of coupling between the rotor blades and the covers, a position of coupling, and so on are proposed as for the whole periphery integral blade structure. As an example, a turbine rotor blade including rotor blades in which a torsion preventing piece is provided at a blade planting part included at a bottom part side of a blade effective part, and a torsion return restricting piece where the torsion preventing piece is to be fitted is provided at a turbine wheel planting part is proposed.